Spectrometer with active beam steering

Abstract

A spectrometer includes a light source that emits a beam into a sample volume comprising an absorbing medium. Thereafter, at least one detector detects at least a portion of the beam emitted by the light source. It is later determined, based on the detected at least a portion of the beam and by a controller, that a position and/or an angle of the beam should be changed. The beam emitted by the light source is then actively steered by an actuation element under control of the controller. In addition, a concentration of the absorbing media can be quantified or otherwise calculated (using the controller or optionally a different processor that can be local or remote). The actuation element(s) can be coupled to one or more of the light source, a detector or detectors, and a reflector or reflectors intermediate the light source and the detector(s).

The invention claimed is: 
     
       1. An apparatus comprising:
 a light source configured to emit a beam into an open path volume containing an absorbing medium; 
 a first detector configured to detect at least a portion of the beam emitted by the light source, wherein the light source and the first detector are disposed on opposing sides of the open path volume; 
 at least one actuation element configured to selectively cause the beam emitted by the light source to be steered; and 
 a controller in communication with the at least one actuation element, the controller configured to:
 determine that a path of the beam should be steered based on at least one of an intensity level and/or a position of the beam detected by the first detector; 
 identify a divergence of the path of the beam and/or optical diffraction and/or an interference along the path of the beam; and 
 cause the at least one actuation element to steer the beam to adjust the position and/or an angle of the beam to correct the divergence and/or the optical diffraction and/or the interference along the path of the beam in response to the position and/or an angle of the beam detected by the first detector. 
 
 
     
     
       2. The apparatus of  claim 1 , further comprising a beam splitting element and a second detector, wherein the beam splitting element is disposed along the path of the beam between the light source and the first detector and is configured to direct a first portion of the beam to the first detector and a second portion of the beam to the second detector. 
     
     
       3. The apparatus of  claim 2 , wherein the first detector and the second detector are the same type of detector. 
     
     
       4. The apparatus of  claim 2 , wherein the first detector is configured to generate a signal representative of the intensity level of the first portion of the beam, and the second detector is configured to generate a signal representative of the position of the second portion of the beam. 
     
     
       5. The apparatus of  claim 2 , wherein the first detector and/or second detector includes an array of photoreceivers, a multi-element photoreceiver, a quadrant detector and/or at least one position sensing photodiode. 
     
     
       6. The apparatus of  claim 2 , wherein the first detector and/or second detector include an indium gallium arsenide (InGaAs) detector, an indium arsenide (InAs) detector, an indium phosphide (InP) detector, a silicon (Si) detector, a silicon germanium (SiGe) detector, a germanium (Ge) detector, a mercury cadmium telluride detector (HgCdTe or MCT), a lead sulfide (PbS) detector, a lead selenide (PbSe) detector, a thermopile detector, a multi-element array detector, a single element detector, a CMOS (complementary metal oxide semiconductor) detector, a CCD (charge coupled device detector) detector, and/or a photo-multiplier. 
     
     
       7. The apparatus of  claim 1 , wherein the light source includes one or more of a tunable diode laser, a tunable semiconductor laser, a quantum cascade laser, an intra-band cascade laser (ICL), a vertical cavity surface emitting laser (VCSEL), a horizontal cavity surface emitting laser (HCSEL), a distributed feedback laser, a light emitting diode (LED), a super-luminescent diode, an amplified spontaneous emission (ASE) source, a gas discharge laser, a liquid laser, a solid state laser, a fiber laser, a color center laser, an incandescent lamp, a discharge lamp and a thermal emitter. 
     
     
       8. The apparatus of  claim 1 , wherein the at least one actuation element is coupled to the light source, a transmissive optical element and/or the first detector. 
     
     
       9. The apparatus of  claim 1 , wherein the absorbing medium includes a gas, a liquid, a reflective media, an emitting media, and/or a Raman active media. 
     
     
       10. The apparatus of  claim 1 , wherein the at least one actuation element includes at least one piezo element. 
     
     
       11. The apparatus of  claim 1 , wherein the at least one actuation element comprises a stepper motor, an electro-optical actuator, an acousto-optical actuator, a micro-electro-mechanical systems (MEMS) actuation device, an inch-worm, a mechanical actuator, a magnetic actuator, an electrostatic actuator, an inductive actuator, a rotary actuator, a heated actuator, a pressure actuator, a stress and strain actuator, and/or an analog motor. 
     
     
       12. The apparatus of  claim 1 , wherein the at least one actuation element comprises or is coupled to a prism, an etalon, a lens, one or more gratings, a diffractive optical element, a reflector, a birefringent element, a crystal element, an amorphous element, an electro-optic element, an acousto-optic element, an optical window, an optical wedge, a waveguide, an adjustable waveguide, an electrically manipulated waveguide, and/or an air waveguide. 
     
     
       13. The apparatus of  claim 1 , wherein the steering of the beam includes adjusting the position of the beam in accordance with a pre-defined x-y position and/or adjusting the angle of the beam in accordance with a pre-defined x-y angle. 
     
     
       14. The apparatus of  claim 1 , wherein the controller is further configured to cause the at least one actuation element to maintain the position of the beam at a pre-defined x-y position and/or maintain the angle of the beam at a pre-defined x-y angle. 
     
     
       15. The apparatus of  claim 1 , wherein the open path volume is a process line, pipeline, tube, channel, duct, stack, tank and/or container. 
     
     
       16. The apparatus of  claim 1 , wherein the open path volume defines an area and/or a boundary within the ambient environment to be monitored. 
     
     
       17. A method comprising:
 emitting, by a light source, a beam into an open path containing an absorbing medium; 
 traversing the open path by the beam a single time in an open path system configuration; 
 splitting the beam emitted by the light source into a first portion and a second portion using a beam splitting element; 
 detecting, by a first detector, the first portion of the beam; 
 detecting, by a second detector, the second portion of the beam; 
 determining, by a controller, that a path of the beam should be steered based on at least one of an intensity level and a position of the beam, the determining including identifying a divergence in the path of the beam, an optical diffraction along the path of the beam, and/or the interference along the path of the beam; and 
 selectively steering, by at least one actuation element in communication with the controller, the beam to adjust a the position and/or an angle of the beam, the position and/or the angle of the beam being adjusted to correct the divergence, the optical diffraction, and/or the interference, the beam being steered in response to the position and/or the angle of the beam as determined by the first portion of the beam detected by the first detector. 
 
     
     
       18. The method of  claim 17 , wherein the open path is defined by a process line, pipeline, tube, channel, duct, stack, tank and/or container or by a boundary of an area within the ambient environment to be monitored. 
     
     
       19. The method of  claim 17 , wherein the first detector is configured to generate a signal representative of the position of the first portion of the beam, and the second detector is configured to generate a signal representative of the intensity level of the second portion of the beam. 
     
     
       20. The method of  claim 17 , wherein the at least one actuation element is coupled to the light source and/or the second detector.